The present invention relates to a lens barrel designed to move a prescribed lens group to a position where the optical axis of the prescribed lens is different from that of another lens group at the time of retraction, and an image pickup apparatus provided with the lens barrel.
What is commonly known in the prior art includes a lens barrel which is retracted by reducing the interval between lens groups in an image pickup optical system in order to improve portability, when not used for photographing.
One of recent disclosures for further minimizing the thickness of the retracted barrel includes a lens barrel where a prescribed lens group is moved to a position where the optical axis of this is different from an optical axis of another lens group as well as the interval between lens groups is reduced (e.g., the Japanese Unexamined Patent Application Publication No. 2004-233916).
A common mechanism for moving a prescribed lens group to a position where the optical axis of this is different from that of another lens group generally has the following structure. As described in the aforementioned Patent Application Publication No. 2004-233916, a lens frame for holding the prescribed lens group is supported by a shaft in such a way that the frame can be swung, and is biased by a spring. This lens frame is brought in contact with a stopper and is stopped at a position where the optical axis agrees with that of another lens group. At the time of barrel refraction, a cam is engaged with the lens frame to make it to be swung against the bias pressure of the spring, whereby lens retraction is performed.
In the aforementioned lens barrel where a prescribed lens group is moved to a position where the optical axis is different from that of another lens group whereby lens retraction is performed, it is a common practice that a spring bias force is constantly applied to the engaged cam at the time of lens retraction. When this structure is exposed, for example, to a high temperature for a long time with the spring bias force applied thereto, the cam may be deformed by the bias force on a rare occasion if the cam is made of resin and is comparatively fragile. As a result, the lens frame may fail to perform a desired swinging operation and this problem has been one of the causes for reduction in operation reliability. Further, in a proposal for solving these problems, the cam is made of a metallic material. However, this fails to solve the problem of increased costs.
In view of the problems described above, it is one of the objects of the present invention to provide a thin lens barrel of high operation reliability at a reduced cost.